"Mitt Romney won't sweep the 10 states that vote on Super Tuesday," says Jonathan Martin at Politico. But with 437 delegates at stake in Alaska, Georgia, Idaho, Massachusetts, North Dakota, Ohio, Oklahoma, Tennessee, Vermont, and Virginia, today gives Romney his best shot yet "to reaffirm his inevitability as the GOP's presidential standard-bearer." Romney stands to clean up in Massachusetts (where he served as governor) and Virginia (where Newt Gingrich and Rick Santorum failed to even get on the ballot), but elsewhere, Gingrich and Santorum will be fighting hard to prove they deserve to stay in the race, and Ron Paul will continue his quest to rack up as many delegates as possible. Here, a guide to Super Tuesday's five most important races:

1. Ohio
Delegates: 66

Who's favored to win: Romney... but just barely

Why it matters: Ohio "is the consensus choice as the biggest prize on Tuesday," says Kyle Leighton at Talking Points Memo. Ohio is a crucial November swing state, and today's results will prove a key test of general election viability. Santorum has been campaigning hard in Ohio, but Romney has essentially erased Santorum's lead in the polls, and if he wins the popular vote, it's a big step toward knocking Santorum out of the race. Either way, thanks to Santorum's failure to get on the ballot in key districts, Romney is "the favorite to take the plurality of delegates," says Nate Silver at The New York Times.

2. Georgia
Delegates: 76

Who's favored to win: Gingrich

Why it matters: Forget Ohio — with its 76 delegates, the Peach State is "the most important contest on Super Tuesday," says Matthew Dickinson at Presidential Power. All the polls have native son Gingrich winning the statewide vote by double-digits, but don't overlook "Georgia's capacity to surprise." The biggest Georgia shocker might be Santorum's big fade, says The New York Times' Silver. Gingrich has named this his must-win state, and he looks likely to win big: 56 delegates, to Romney's 17, and Santorum's paltry 3. That means, if our projections hold, Gingrich will score more delegates than Santorum on Tuesday. Ouch.

3. Tennessee
Delegates: 58

Who's favored to win: Too close to call

Why it matters: The race in Tennessee is "the new hotness," says John Putnam at Frontloading HQ. Romney has narrowed Santorum's big lead to 4 percentage points, and "Gingrich is closing even faster," says Silver. "A Romney win in Tennessee would be second only to Ohio in symbolic importance," says Politico's Martin, proving he can "win in a culturally Southern state." If Romney pulls this off, adds Putnam, it will be "a backbreaker in a lot of respects for the Gingrich and Santorum causes."

4. Oklahoma
Delegates: 43

Who's favored to win: Santorum

Why it matters: Oklahoma is "Santorum's strongest state," but as in Tennessee, he's slipping as Gingrich and Romney gain, says The New York Times' Silver. As a result, Santorum will likely fall short of the 50 percent threshold that would automatically award him 40 delegates — a cushion he could really use, given his slippage elsewhere. The big story is that Gingrich "has quietly pulled himself into contention in Tennessee and, possibly in Oklahoma," says Dickinson at Presidential Power. The Sooner State polling isn't recent enough to catch the "Newt surge," but watch to see how much he outperforms projections here.

5. North Dakota
Delegates: 28

Who's favored to win: Too close to call

Why it matters: The exciting thing about North Dakota's caucuses is that anybody could win, says Micah Cohen in The New York Times. There hasn't been any polling of Super Tuesday's three caucus states, but while Romney has a good shot at winning in Alaska and Idaho, Paul and Santorum each have "a solid chance to defeat him" in North Dakota. Santorum has done very well in prairie states, and Paul "has been organizing in North Dakota since November." North Dakota's caucus is also open to any voter, says Politico's Martin. "Translation: This is Ron Paul's best chance to score a victory Tuesday."

Sources: Frontloading HQ, Green Papers, Huffington Post, MSNBC (PDF), New York Times (2, 3), Politico (2), Presidential Power (2), Talking Points Memo